This invention relates to a radiation detector.
Diamond can be used to respond electrically to radiation which penetrates only a small distance (eg. less than 10 μm) into diamond, such as alpha particles and electromagnetic radiation with a wavelength of less than approximately 220 nm, e.g. ultra-violet and soft X-rays. Current diamond detectors for such radiation consist of a thin layer of diamond, generally about 1 to 200 μm in thickness of as-grown diamond, either free-standing or a non-diamond substrate such as a silicon substrate. Typically, the growth surface of the thin layer will be patterned with an interdigitated electrode array.
Diamond is a wide band gap semiconductor and at room temperature it is, under normal circumstances, an electrical insulator. For a pure diamond to conduct, electrons must be promoted from the normally full valence band to the normally empty conduction band, creating electron-hole (e-h) pairs; this occurs when radiation such as gamma-rays, X-rays, ultra-violet light, alpha particles and beta particles impinges on the diamond. If there is an electric field across the diamond, the carriers will move and a current, the photocurrent, will flow. The size of the photocurrent for a particular diamond will depend on the type and intensity of the radiation and it will flow until the e-h pairs recombine.
The charge carriers which are produced by the radiation are typically collected by the interdigitated electrode array on the growth surface of the layer.
U.S. Pat. No. 5,216,249 describes a neutron detector comprising a layer of polycrystalline diamond material deposited by chemical vapour deposition, the diamond material containing sufficient amounts of 10B as a dopant to optimise the neutron detection characteristics of the detector,